I find this statement almost amusing, “...FBI and DOJ leaders who are demanding to see it [the HPSCI four-page memo].” After months of stonewalling congressional committees’ requests for information, they “demand” anything of Congress? I’m afraid I’d have to tell Sessions and Wray, “F**k you, nasty letter follows...”
If that's the case, they already know what information is contained in the Republican-written memo. It's their own information.
So why do they want the release of the memo stopped? So they can redact the hale out of it and give some of it to Mueller to redact. No doubt the contents are damaging to themselves and not to national security.
But the biggest problem I see in this deal is what you identified in your comment.
It is the Congress that has oversight over the DOJ and FBI, not the other way around. The DOJ and FBI have no authority to tell congress what to do or not to do. They are the tail and the congress is the dog.
So why are we letting the tail wag the dog in this case?